1. Field of the Invention:
The present invention relates to an air cleaner for use with an internal combustion engine.
2. Description of the Prior Art:
An air cleaner for use with an internal combustion engine generally includes an annular filter element, wherein the air which is introduced into the filter element from the outer peripheral portion thereof traverses the filter element in the radial direction and after the dust etc. contained therein is removed, the cleaned air reaches an outlet chamber space formed at the central portion of the annular filter element. From this chamber the clean air is drawn into an intake tube incorporating a carbureter, etc., of an internal combustion engine.
On the other hand, gas which leaks out of a combustion chamber of an internal combustion engine through a clearance between a piston and a cylinder wall is called blow-by gas which remains in the crank case. This blow-by gas is fed from the crank case to an intake manifold by way of a PCV valve so that it is reintroduced into the combustion chamber. In this case, in order to avoid vacuum being generated within the crank case due to a vacuum in the intake manifold, the crank case space is connected to the outlet chamber space of the filter element in the air cleaner by way of a conduit means. However, when the engine is operating in a high speed and high load condition with a corresponding increased amount of the blow-by gas, or when the PCV valve has failed to open, a positive pressure is generated in the crank case, whereby the blow-by gas flows into the air cleaner by way of said conduit means. In this case, if stagnation of the blow-by gas is generated in the air cleaner, the filter element is contaminated, whereby the intake efficiency and the output power is lowered, causing an unfavorable affect on the quality of the exhaust gases.
Furthermore, in modern vehicles, many of which are equipped with an air pump to purify the exhaust gases, if the intake air for the air pump is taken from the outlet chamber space of the filter element of the air cleaner for the engine, an air intake port for the air pump will also be opened to said outlet chamber space. In the case where these two ports, one communicating with the space within the crank case of the engine and the other communicating with the intake port of the air pump, are simultaneously opened to the outlet chamber space of the filter element, if the blow-by gas has been blown into the air cleaner, a large amount of oil mist contained in the blow-by gas is drawn into the air pump, whereby wear on carbon shoe supporting vanes of the air pump occurs, thereby producing abbrasive powder which causes still further wear of the carbon shoe. This abnormal wear on the carbon shoe results in a rattling rotation of the rotor and, ultimately, failure of the vanes. It is generally recognized that if oil of about 1cc/hour is introduced into an air pump, the air pump lifetime is shortened to one tenth of normal expectancy.